


Childish Misunderstandings

by SkellyTelly



Series: For Others [3]
Category: Undertale (Video Game)
Genre: Family Feels, Fluff, Gen, Hurt/Comfort, Mpreg, Papa Gaster, Pregnancy, baby bones sans - Freeform, off screen childbirth, single parent gaster, skelepreg
Language: English
Status: Completed
Published: 2018-05-29
Updated: 2018-05-29
Packaged: 2019-05-15 08:30:52
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,770
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/14787012
Author URL: https://archiveofourown.org/users/SkellyTelly/pseuds/SkellyTelly
Summary: Gaster plans to have another baby, but will Sans know what that means?





	Childish Misunderstandings

**Author's Note:**

> For Lycovore on Tumblr!

Things were great for little, young Sans and his papa, Gaster. That kid didn’t have a care in the world. They had a sturdy routine which was followed religiously: wake up, breakfast in the morning, get dressed for work and school, did their own things, at dismissal Sans was picked up by Gaster, the two would go home together and make dinner, and then after that it was free time before bath, brushing teeth, changing into PJs, and going to bed with a story. And whenever school wasn’t in session, Sans was going to work with Gaster.

 

Sure the labs weren’t the best place for a child, but Sans had a good sense to stay clear of the danger zones. He was allowed to observe from a safe distance behind glass though. Science was something that absolutely thrilled the child. Seeing them work on those big mechanical machines, writing out large diagrams on rolled out blue paper, discussing the process of using X and Y to make Z. Sure it was way over Sans’s head, but he liked to listen in.

 

One particular conversation caught Sans’s attention, as while the adults were discussing a new project… Sans’s name popped up somewhere in there from Gaster. Sans had not really picked up on what they were saying but began listening to the moment after.

 

“-I’ve recovered now, so this could be the best time for it.” Gaster presented to his colleagues.

 

The other adults were quietly listening to Gaster, though they exchanged some concerning glances, one of the fellow scientists spoke up, “Dr. Gaster, are you… Really sure? I mean, while the first trial was technically a  _ success _ .” Their hand gestured over to Sans, “Back then you had less responsibility on your shoulders and it  _ still _ resulted in premature labor.”

 

It was way over Sans’s head what any of this meant or what they were talking about, he just sat in the chair off in the corner of the room with his play model rocket ship. He looked back to Gaster, who had been struggling to make a counterpoint.

 

“... Dr. Gaster?” The scientist inquired.

 

“... If I may be so bold, this is less really for the benefit of the experiment and project… And more a benefit for  _ myself _ .” Gaster said, which seemed to shock the other assistants sitting around the table.

 

“Doctor,” Another assistant, who pushed their glasses up on their nose then questioned, “Are you perhaps trying to tell us that you…  _ Just want to have another child? _ ”

 

For once, this was a discussion that Sans was able to follow intently, little eyes wide and curious as he looked back onto his father.

 

Gaster, ever in his usual awkward manner, ducked his head down bashful and demure, “Mmm… Yes, yes that is exactly what I’m saying.”  
  


* * *

 

 

Sans had been pretty confused by that whole conversation.  _ Another child? _ Like him? On the walk home that evening, Sans held on the Gaster’s black coat while they made the trek home. Though just as they turned the corner and were in view of their house-

 

“Papa, are you going to replace me?”

 

Gaster took only one more step, before freezing up in place, standing there like a stone statue. Those words lingered in the air for a deafening moment, before Gaster looked down to Sans, “... Replace?”

 

“You want another kid.” Sans tugged a little more on Gaster’s coat, “Y-you… You’re done with me?”

 

The very moment Gaster saw just a budding of tears to Sans’s eyes, he was frantically hopping from foot to foot and dropping to his knees, scooping up the small child in his arms, “ _ A-ah! _ Sans!  _ Sans sans sans _ -no! That’s not it at all!”

 

Sans was already sniffling into Gaster’s button up shirt, little fingers reaching up to hook onto the front pocket.

 

Gaster stayed there on his knees and petting Sans’s back, “Sans, I… I was going to explain this a little later, but- _ suppose you did hear the most of what was going on _ .” For some reason, Gaster was counting on Sans to not even bother listening to that discussion from earlier, at least he seemed not to be paying any mind to it, “No Sans, you’re not being replaced. You’re never to be replaced.”

 

Big, glimmering, teary eyes looked back up to Gaster, far more at ease with that said just now, but still on the verge of spilling out sobbing.

 

“You’re my  _ Sans _ . My  _ first born _ and forever will be that.” Gaster gently thumbed those tears to threaten falling down Sans’s cheeks, “No no… This is actually exciting news, Sans…” Gaster looked to the side, a little nervous now, but went on ahead to speak, “I’ll be having a baby, and you’ll be a big brother.”  
  


* * *

 

Once Sans was back in school, his new claim to bragging fame was to spread the word amongst his school pals that he would soon become a  _ big brother _ . Which, for any younger sibling classmates, were pretty impressed and fairly jealous. Sans could take the credit of being one of the only ones there to be the  _ first _ big brother and not have the title claimed by having an older sibling of his own.

 

The prospect brought as much excitement to Sans as it did for Gaster, what event prompted this big decision was Sans starting school. Ever since Sans adapted so well to going to school, it was quite symbolic of how much Sans had grown. Gone were the days of Sans needing to be rocked to sleep and read simple bedtime stories. Now the kid was starting to read books to himself.

 

Gaster needed to cradle another sleepy baby in his arms, wanted to cuddle with them and dress them up in all the most ridiculous outfits and not have  _ said child _ protest. And furthermore, the family dynamic had only been him and Sans so far. Gaster prides himself on choosing the single parent life and taking it in stride. With Sans’s growing independence, Gaster feels it would be safe enough this soon to bring in a new addition. Besides, he’s already got a little experience with this roadeo so it might go a lot easier this time around for him than it did before, right?

 

…  _ Riiight _ ?  
  


* * *

 

Well, morning sickness came in like a freight train. The good news was, he was definitely pregnant only after one trial of insemination (through soul magic), but the bad news comes from the fact that Gaster took on the worst bout of morning sickness he had never before encountered.

 

At the crack of dawn, he was rolling out of bed, feeling the world spin around him, stumbling off to the bathroom, just barely making it in time too. It wasn’t a great start to the morning. He could not handle brushing his teeth, the smell of mint being an egregious smell that he gagged, the best he did was rinse his mouth out.

 

And then came breakfast as Sans was still needing a good meal before getting up and ready for school.

 

Sans sat at the table, kicking his legs in the air while up on one of the dining chairs. Gaster was in the kitchen and opened the fridge. Just  _ looking _ at the carton of eggs made his stomach want to flip upside-down. And orange juice might as well have been battery acid, the thought of its very taste, usually, a pleasant one, has him feeling queasy.

 

What Gaster ended up bringing out for Sans was… A simple bowl of cereal. As for himself: dry toast.

 

The young child watched his green-tinted parent set the bowl in front of him, and saw how his movements from standing to sitting down were slow and cautious. Sans looked from the table to Gaster, “... Papa? Where’s my juice?”

 

Gaster nibbled on a corner of the bread, tiredly lifting his weary head up to Sans.

 

“Orange juice?” Sans insisted.

 

Gaster just barely swallowed that small bite of bread, feeling horrendous at that alone, “... We ran out.”

 

Morning sickness was a trip and a half, making Gaster easily gag over anything with just the slightest bit of smell to it or with the slightest texture of anything soggy. He stuck with bland and dry, that seemed to be the most his stomach could handle, he’d be lucky if he had a hot meal. This unfortunately translated to Sans’s meals too.

 

In Sans’s curious questioning of “ _ Why are we only eating toast and granola bars? _ ” Gaster finally just relayed the honest truth that he was just very sick and could not be brought to do it.

 

One evening as Gaster was napping on the couch, or rather  _ trying _ to as he was becoming restless by the mere  _ all day sickness _ he was just constantly afflicted with, Sans came down from the upstairs, carrying with him a bundled up blanket and a stuffed bunny.

 

“Here, papa.” Sans put the bunny aside, taking the blanket then to unfurl and toss over Gaster, pulling the edges to cover his father the best he could, “When I got sick, you covered me with blankets and gave me fluffy bunny to-to feel better.” He then tucked the rabbit by Gaster’s head.

 

Gaster felt like crying, giving just a proud smile and reaching out to pat Sans’s head.

  
  


* * *

 

With the help of generous co-workers, Sans was sure to not go without proper meals while Gaster was unfit to cook. With his  _ lamenting _ -rather  **_reporting_ ** to his fellow assistants of how his physical well being was performing at that early stage of the pregnancy, they noted that some intervention was required. For one, they were sending him home with a couple easy to prep and serve meals for little Sans to enjoy and some left over for Gaster. 

 

He began to steadily improve over time with some help of vitamins. This was just the first step they wanted to take that would hopefully help Gaster to reduce the severity. Sure it took awhile, but with the vitamins’ help, Gaster showed slow improvement.

 

And then came the growth period.

 

Sans was more than ready for Gaster’s sickness to end and suddenly have a baby emerge! Except that wasn’t the case. And Gaster had to sit down and explain it to Sans:

 

“ **_Nine months!?_ ** ” Sans startlingly repeated.

 

“It’s already been about four months now, so we only have to wait… Hm… Five more months?”

 

“That’s going to be  **_forever_ ** ! I wanted to bring the baby to show-and-tell!”

 

Gaster merely shook his head, “Sans, the baby needs time to grow, we must be patient with--”

 

“Just make it come early!”

 

Ahh, children and their inability to understand the concept of time. Five months may just as well be five  _ years _ , the lives of children spanned for eons and eons more. Five months for adults, such as Gaster, saw it as a drop in the bucket. And with that, all considered, Gaster was no longer going to engage in this argument with Sans, namely because the said toddler was starting to throw a retroactive tantrum over something Gaster could not physically act upon and rectify.

 

Sans probably kicked, rolled on the floor, and cried for a solid ten minutes while Gaster tended back to his business of separating the colors from the whites and dumping the laundry into the washing machine to clean.

 

Gaster could hear Sans’s cries grow fainter, reducing to sniffles and an occasional whine to try and kick off the emotions again.

 

Standing there and pulling out the laundry, Gaster felt something grab onto his pants leg, a rather cry-exhausted child just sniffled and hugged on tightly. It was something that Gaster could not resist. He knelt down to Sans’s level, bringing him into a comforting embrace.

 

“Sans, I’m sorry if I led you to believe any different,” Gaster apologetically petted Sans’s head, “... If I could have it sooner, I would have, but that’s just not possible. I’m sorry, son. OK?”

 

After a calm silence, Sans’s mouth quivered, eyes sprung tears anew, and gave another pitiful cry while going limp in Gaster’s arms.

 

He tried.

 

* * *

 

While Sans did have some strong expectations for the arrival of his younger sibling, he soon just accepted the truth of the matter but still didn’t fully understand it. And this was strongly made apparent during one evening Sans saw Gaster without some kind of coat or sweater on.

 

Gaster noticed Sans’s staring from across the room while sitting on the couch, he was not looking at the TV at all and just stared wide eyed at his papa. Which got Gaster a little antsy.

 

“Um… Son?” Gaster meekly called over.

 

Sans was merely silent, pushing himself off the edge of the couch cushion and trotting right on over to Gaster. Standing at this angle, as Sans came up to about Gaster’s hips, the swell of Gaster’s belly was level to Sans’s head.

 

“... Sans?”

 

Sans put his little hands on the tummy, “When did THIS happen?”

 

Gaster smirked, surprised and all at once broke out into laughter, belly bouncing with his guffawing.

 

“What did you  _ eat _ ??”

 

Oh, Gaster was just doubling over now, working hard to reclaim himself, but even as he breathed and put a hand on Sans’s shoulder, he was cracking up with more giggles and by this point brought to tears.

 

“S-sans-oh angel-Sans, son…” Gaster’s laughs kept interrupting now and then but were petering off and he sighed with relief, “That’s the baby, remember?”

 

The look on Sans’s face was that of some horror, “You… YOU **_ATE_ ** THE BABY!?”

 

Gaster dropped his head, barking out more laughs.

 

“I didn’t even get to MEET them and you ATE them!? How could you??” The pure innocence Sans had made his voice of betrayal so pure and tangible.

 

All between the crying and laughs, Gaster had to try and recover the situation with profusely denying those accusations. At some point, Gaster ended up on the floor and had his head in his hand while holding Sans close with the other.

 

“ _ Eehehheh-- _ Oh! Heh-oh Sans, Sans-” Gaster finally sniffled and bumped foreheads with the young tot, “Sans, they’re OK, give me your hand.”

 

Sans may be pouty and glaring at Gaster still, but he did comply and hold up his hands, which then Gaster took and brought right back down to his bump. After a moment of pressing Sans’s palm to his belly, there was a strange sensation that came from underneath the shirt.

 

“You feel that?” Gaster asked.

 

After another instance of feeling it happen, Sans looked to Gaster and nodded.

 

“That’s the baby, kicking their little feet.” Gaster said, helping to guide Sans’s hand to where exactly the most bumping and nudging could be felt, “It’s as I told you, they’re growing… _Except maybe I should have specified_ **_where_**.” Again, Gaster just kinda assumed Sans understood, but it seemed to become better understood now that there was an actual visual example, “They’re safe and sound, and in a couple more months, they’ll come out!”

 

All while being told this, Sans just kept feeling papa’s tummy, fingers splayed and every so often there was a small tap or a rolling. He long since forgotten that he was upset now, and just curious and wondering.

 

* * *

 

As Gaster got bigger, clothes got smaller, and fewer things were left in his wardrobe that he could properly wear over his globe of a belly. Life also got a little more difficult the bigger that Gaster got. Walking was a challenge, he was easily fatigued and was not as easily able to get up from sitting down as he once had. He managed this all before Sans was born, but now he was responsible for more than just himself, so he had to keep up with the routine in place while somehow also navigating with a watermelon under his shirt.

 

Sans was rather helpful in the ways Gaster could only ask him to be, whether that was going to grab something from the other room or having Sans be independent and do things on his own, Sans was readily available and willing. There was still hardships to overcome with being an expecting single parent.

 

Gaster got a call from Sans’s school.

 

Sans broke his arm.

 

Apparently, as it was relayed to Gaster, the children were playing in the courtyard of recess, and one game of “humans and monsters” resulted in Sans, acting the role of a “human” getting pretty roughly tackled to the hard stone cut ground and yowling out in pain as there was no doubt a fracture that was clearly visible to his arm.

 

Gaster arrived at the school, the nurse had already taken care of bracing Sans’s arm and healing any HP lost in the scuffle. There was no sign of this being a case of bullying, just kids getting too rowdy and caught up in their imaginations. Small scrapes that Sans got were simply healed, but to ensure his arm was better, a night’s rest was in order and some good, magic-infused food.

 

Thankfully, skeleton monsters could treat fractures much like a cut: bandage it and allow it to heal on its own. Though the pain was still no less that of a real bone fracture.

 

Gaster carried Sans’s backpack as they made the slow walk back home, Sans’s arm was already put in a makeshift sling too. Along the walk though, Gaster slowed more and more, finally just stopping altogether.

 

“... Mh? Papa?” Sans’s little voice was a bit raspy, from all the crying and yelling earlier, the little tyke was pretty worn out.

 

Looking back up to Gaster though, Sans saw him… Crying?

 

“Papa??” Now Sans was worried, seeing Gaster drop down to his level, and quickly reach out to hug him, “ _ Ow! _ ”

 

Gaster quickly lets go, but seeing that Sans was not too hurt from the incorrect hugging method for a small skeleton with a broken arm, he then carefully slipped his arms around Sans in a fashion to hug him much more comfortable, even if it was a bit awkward with the pregnant belly getting between them.

 

“What’s wrong??” Sans was not pulling out of the hug by any means, it was actually much appreciated after the time he had just been through, but papa was so upset out of nowhere.

 

“ _ I..I’m s-suh-rr-sor-rr-ry, _ ” Gaster choked out, hugging Sans just a bit tighter and gave some quiet sobs.

 

For as calm and collected Gaster was when arriving at the school and pulling Sans out of class for the rest of the day, internally he was shrieking with feeling on the constant verge of tears. He actually seemed pretty cold and stern when he arrived to sign out Sans, intimidating some of the staff into assuming he may want to yell at them for being negligent and demanding some form of apology from the other child in question. Which was why they were quick to debunk any concern of this being a purposeful attack.

 

And sure, for a hot minute, Gaster was fuming and as with that, kept it internalized to not make a scene… Except now that they were finally in a pretty lonesome clearing, Gaster’s emotions spilled over and he finally began to just cry.

 

He cried with relief, but also releasing the emotions of intense worrying he had while picking Sans up. Despite being told that Sans would be fine, Gaster feared for the worst upon arriving, and it only spurred several other  _ darker thoughts _ that Gaster never wished to remotely entertain in his entire life.

 

“Papa, I’m OK!” Sans insisted to try and calm his sobbing parent.

 

Gaster just held Sans’s head, nuzzling the top of his skull. It would be a few more minutes of this constant sobbing before Gaster finally composed himself enough to stand back up and continue their walk on home.

 

* * *

  
  


Late into the night, days prior to Gaster’s official due date, he was sleeping well and fine in bed. The faint ticking of a clock is the only audible thing through the dark silence of “night” in the Underground.

 

Sometime during the night though, Gaster unexpectedly woke. He was dreaming one moment, and then suddenly his droopy eyes were barely peeking open. The room with pitch black, shapes just barely visible with the faint glow that seeped through the window curtains. There was no reason he saw in waking up, so he pulled the blanket up over his shoulder to tuck himself back into bed.

 

Though sleep just wasn’t coming. In fact, instead, he started to feel a bit queasy. His stomach was in knots, and he wasn’t sure why. Though with how unpredictable pregnancy was, he was not really able to just wait this out. He pushed the blankets off, slow to rise up in bed… And then that knotting in his stomach got tighter, to the point it was sharp and painful.

 

Gaster choked on his breath, this tension made it hard for Gaster to focus, after a couple seconds in, he tried to mentally count out how long this blinding pain was lasting. His counting method of trying to evening pace the numbers was too difficult and this pain lasted long enough for him to just assume it was the real gig.

 

What lovely timing, just as he had been trying to get a good night’s sleep. He could at least look over his nausea now and work instead towards calling up some help. Given the nature of the pregnancy’s conception, rather than seek out the hospital, the lab was instead prepared and equipped to deliver this baby. Though as a fail-safe, a midwife had been recruited to assist.

 

Gaster’s pacing and talking over the phone must have been enough to stir awake Sans since Gaster arrived into his room with him already awake.

 

“ _ Mmh? _ ” Sans raised a little fist to rub his sleepy eye.

 

“Come along, Sans, we need to get to the lab.” Gaster wasted no time in going to the coat hooks by the dresser to grab Sans a coat and some boots, “No time for anything else.”

 

“ _ Iz’it mor’in’? _ ” Grumbled a sleepy child as he slowly got out of bed.

 

“Lab. Now.” Gaster slipped the jacket on Sans and got down on his knee to get Sans to step into one boot at a time through the dark.

 

“ _ Whu? _ ” Still, in the daze of tiredness, Sans was being dragged along and having little understanding of where they were or what was going on.

 

Just as the walk from home to school was short, the walk then to the Lab was just a bit more. Along the hurried speed walking, Gaster had to stop a couple times and double over in agony. Sans just assumed it was that Gaster was out of breath with how heavy of breathing he was doing during those stalling moments before quickly picking up the march again.

 

And with little time left to spare, they got to the lab, right there at the front door was one lab assistant readily waiting.

 

“Dr. Gaster!” They called out, running over to his side and offered a shoulder of support for Gaster to hold onto.

 

OK, now this started to actually worry Sans, he looked at the lab assistant rather confused, they seemed to be highly  _ concerned _ for Gaster… Was there something wrong that Sans wasn’t seeing?

 

“Papa??” Sans’s pitch went up with concern.

 

“Inside. Inside now.” Gaster just barely managed to demand before another contraction took place and he was stumbling even with the assistant’s assistance.

 

The three hurried on in, where other staff were waiting, though they all turned white as ghosts with how dire Gaster’s appearance looked. Wheeling a wheelchair over and sitting Gaster down to then rush him off to the elevator. Sans got a little lost in the whirlwind of lab coats flurrying around him that he saw the elevator doors closing and began to panic.

 

“WAIT! WAIT!” Sans cried out, running just as the doors shut.

 

Two scientists that stayed up there took notice to Sans, “Oh! Thank goodness-there you are!” The one female co-worker of Gaster’s came to Sans’s side.

 

“Papa! Papa wait!!” Sans tried in vain to pound and pull at the elevator doors.

 

“Sans- _ Sans! _ ” The co-worker’s shrill tone startled Sans to pay attention, she quickly recomposed herself, as tensions were high from the panic that just happened here on the first floor of the lab, “Sans, it’s OK, Dr. Gaster-your dad? He’s going to be alright.” She pushed back some stray hairs from her face to instead tuck behind some protruding horns on either side of her head, “Just calm down, OK? It’s going to be just fine, OK?”

 

“ _ You _ need to calm down.” The other scientist now spoke up to their co-worker, and then kneeled down on the other side of Sans to level with him, “Look kiddo, your dada’s having that baby now, and we gotta wait up here until they tell us we can come down, y’hear?”

 

Sans was trembling, he was certainly not a fan of just being left in the lab with anyone other than his papa. He didn’t want to be left up here all by himself. So, just as any other child will do when in an uncomfortable place around people that were still not that close…

 

Sans began to cry.

 

* * *

  
  


It actually turned out a lot better than what Sans was fearing, after he started to sob in worry of the sudden circumstances, these two scientists seemed to quickly endear themselves to him. The one who was trying to mediate things between their high strung co-worker and Sans was the one to offer Sans some graham crackers. And then the other scientist looked around to bring back out some papers and pencils, offering Sans the chance to maybe do some drawing while they waited.

 

The two went back and forth offering various distractions and comforts to keep Sans preoccupied. It seemed to help calm his nerves and furthermore helped pass the time by.

 

Eventually, the elevator doors opened, there standing one lone assistant. The child raised their head to see the elevator open.

 

“Sans?”

 

And just like that, Sans abandoned all the fun little art activities he was distracted with to instead bolt over to the elevator and ride it down.

 

Walking through the colorless corridors, passing several white smooth doors, they soon arrived in one, as they approached it though, there was muffled sound of crying that came from behind it. Crying from a baby.

 

The door slid right into the wall, “Dr. Gaster?” The assistant called in.

 

Sans stepped ahead into the room, stopping in place as his drew away from all the tech and gear that lined the walls and filled the space around the center point which was a hospital-style bed, with Gaster lying back and in his arms holding a noisy bundle of blankets.

 

Gaster looked up from what he had cradled in his arms, then trailed his eyes back down to Sans. After a rather displeased cry rattled from the bundle, Gaster looked back down and continued rocking it. 

 

Now Sans took slow steps, creeping over to the side of the bed that had a chair sat right next to it, giving Sans something to climb up on. After a moment of waiting for Papa to speak, Sans did curiously stand to peek over Gaster’s shoulder.

 

In that mass of blankets, there was a disgruntled little face, all scrunched up and crying openly. Gaster was seeming to do his best in comforting the upset child, having not much more control over soothing whatever ailment has befallen them.

 

Sans watched patiently, but was all too eager as he climbed closer to Gaster and leaned in on his shoulder, reaching out to the baby’s face, “No baby, shh!” Sans said, fingers barely reaching over to brush the baby’s cheek.

 

A weak little whine came from the newborn as their crying started to trail off, making cooing whimpers and squirming around in the swaddle.

 

Gaster was… Impressed. He was about to shush Sans to quiet his voice down, but the child seemed to respond well to that alone. It was something that Gaster really could not complain about, having spent these minutes here alone trying to quell their crying on his own. Though now with a subdued infant, he could smile with relief and look up to Sans, “... Wow… You’re quite a natural...”

 

Sans then hugged around Gaster’s neck, “... I missed you…”

 

Gaster leaned his head to Sans, giving a soft exhale through his nose, “Sans?”

 

He lifted his head.

 

“I want you to meet your baby sibling,  _ Papyrus _ .”


End file.
